Signal processing systems, such as radar and sonar systems, are useful for detecting, characterizing and monitoring various kinematic parameters associated with natural and/or man-made objects, and are important for both civilian and military operations. In radar systems, for example, one or more transmitted pulses or electromagnetic (EM) signals are intended to engage one or more objects or targets. Reflected return signals (or echoes) are received and processed for object identification and characterization. Several types of transmitted signals may be used. For example, single pulse, multiple pulse, and LFM waveforms may be used, with each waveform type having particular advantages in terms of target detection and velocity and acceleration estimation, by way of example only.
One strength of LFM waveforms is their tolerance to Doppler mismatch in pulse compression processes. More specifically, Doppler mismatch is an effect that occurs when a received waveform is shifted in frequency away from a transmitted frequency due to target motion (i.e. the Doppler effect). This causes a loss in signal amplitude from an ideal value during pulse compression processing. Tolerance to this Doppler mismatch includes the ability of a waveform modulation to have a minimized reduction in signal level as a frequency shift increases. This contrasts Doppler intolerant modulations which exhibit extreme reductions in signal level.
LFM waveforms, however, experience a range/Doppler coupling effect which results in an ambiguity determining a target's range, as this range is offset by an amount proportional to an unknown velocity. As will be understood by one of ordinary skill in the art, range/Doppler coupling is a phenomenon affecting LFM waveforms that occurs where a non-zero Doppler frequency shift offsets a target's apparent range away from a true target range. The magnitude of the coupling is directly proportional to the pulse length and inversely proportional to the bandwidth of the LFM waveform. If a target's velocity is known this offset can be calculated and removed to produce an accurate range estimate. However, current processing techniques require multiple transmitted and return LFM waveform pulses in order to estimate velocity.
Alternative signal processing systems and methods for estimating velocity from as little as a single LFM waveform pulse are desired.